Patent Literatures 1 to 3 each disclose a friction stir welding device (FSW device) which generates, with a rotating joining tool, a plastic flow in members to be joined and thus joins together the members to be joined.
Patent Literature 1 discloses a friction stir welding device having a structure suitable for three-dimensional joining in which a tool (joining tool) is attached to a five-axis machining center.
Patent Literature 2 discloses a friction stir welding device in which the depth of insertion or the like of a tool (joining tool) is controlled in such a way that the load and current of a main shaft motor for rotating the tool fall within a predetermined range, thus making it less susceptible to the influence of deformation of members to be joined.
Patent Literature 3 discloses a friction stir welding device configured in such a way that a distal end part of a joining tool inserted in members to be joined is swung, thus increasing the width of a plastic flow region and increasing the joining strength.